The present invention relates to a method and apparatus for fixing a rail on a rail-support by using metal spikes which are plastically deformable in torsion or in bending, and to such a metal spike, per se.
Many railroads comprise a pair of rails fixed on wooden ties. A metal sole plate is often interposed between each rail and the ties in order to improve transmission of loads and lateral forces due to trains passing along the rails.
Forged steel spikes or bolts are engaged in the tie on either side of the rail flange, optionally through holes formed in the sole plates. The heads of the spikes or bolts partially overlie the rail flange in order to prevent the rail from lifting or overturning.
The attaching is completed by anticreepers fixed to the rails and to abutments against the ties in order to prevent the rails from sliding longitudinally relative to the ties.
When a worn rail is replaced, it is necessary to extract the bolts or spikes from their holes in the ties, thereby enlarging the holes and damaging the ties. A hole which is excessively damaged cannot be reused and becomes a starting point for rot. If there are not enough spikes or bolts in ties that are in good condition, then there is a danger of derailing.
When tracks are laid, the rails do not bear simultaneously on all of the ties. The resulting clearances are not taken up by the spikes being put into place.
Even when using bolts, rails are not clamped sufficiently uniformly to enable long welded rails to be used which are so advantageous for good track performance. To make that possible, it is necessary to use a resilient attachment comprising a resilient sole plate compressed beneath the flange of the rail by a spring bearing against the top of the flange. Instead of using a spike with a flexible head as the spring, since that prevents rails from being replaced, it is generally preferred to use a resilient fastening which is put under tension by tightening a bolt or by being engaged in a housing of a special sole plate fixed to the tie by independent spikes or bolts. Resilient fastenings allow rails to be replaced without damaging the mounting; however only screw mountings are suitable for adjusting clamping and optionally for subsequent further tightening.
Concrete supports are stiffer than wooden ties. Spikes can be engaged therein. They require a mounting which is more flexible and which necessarily includes a resilient sole plate, with fastenings and lateral abutments interposed between the rail and its support. They are not sufficiently insulating and the mounting must contribute to insulating the rail electrically.
The use of long welded rails is highly recommended for ensuring that shocks at joins between rails do not destroy the adjacent supports. However long welded rails require very uniform clamping in order to prevent buckling due to thermal expansion. All of these conditions can be satisfied by adding additional parts: bolts; washers; insulating spacers; resilient chairs; etc.
Anticreepers are not required when attaching by means of resilient fastenings, whether the attaching is on to wood or on to concrete. However, a large number of parts is always required for assembly on the track. This makes such fastening more expensive and more difficult to perform correctly, whereas it is desirable to reduce the number of parts that need assembling in order to simplify laying so as to make it suitable for mechanization.
A document representative of the state of the art in attaching or fixing systems using spikes is constituted by U.S. Pat. No. 2,869,792. Column 2 lines 22 to 28 thereof describe the possibility of withdrawing spikes only partially and of pivoting them in order to allow a rail to be replaced, with this being made possible by the fact that the bottom portion of each spike is capable of rotating about itself. This constitutes a solution which is difficult to apply in practice since once a rail has been replaced for the first time, it is very difficult, if not practically impossible, to adjust the clamping force or to provide for subsequent reclamping.
Another document is constituted by U.S. Pat. No. 2,195,038 which attempts to solve the problem of providing a fixing system including spikes initially inserted on either side of the rails, i.e. enabling a rail to be laid prior to the spikes being fully inserted into the clamping position, after which, as it is engaged progressively, each spike rotates through 90.degree. in order to take up a clamping position as shown in the righthand sides of FIGS. 1 to 3. This is made possible either by providing the spikes with twisted bodies thus causing them to pivot as they are driven into the support or tie (FIG. 1), or else by providing a cylindrical bottom portion (FIG. 3) making rotation easy.
It will be understood that according to this document, it is indeed possible to pivot the spike from a side position enabling a rail to be put into place to a clamping position, however the major drawback lies in the fact that since such rotation of the spike is easy, the mounting is not reliable and too often trains transmit forces to the rails which cause such spikes to pivot so that they no longer exert sufficient clamping, and in particular the resistance of the rail to overturning is reduced. This is therefore unacceptable.
The object of the present invention is therefore to solve the novel technical problem consisting in providing a fixing system using one-piece spikes which are permanently fixed to the rail support and which simultaneously make it possible to unclamp, remove, and replace a rail, after which the rail is reclamped, and preferably making such operations possible on several occasions without running the risk of the spike rotating in its support when in use. Preferably, this solution should be particularly simple in design so that the fixing method is easy and can be performed by a worker with ordinary qualifications.
The present invention also makes it possible to replace spikes, should that be necessary, and to provide lateral abutment for a rail, when required.
The present invention solves this technical problem for the first time in a manner which is satisfactory, and it can be used on an industrial scale.